Hey Brett...Velocity rollbar "fittings"

[rwhite692]

Anyone know the story about the brackets or fittings holding the downbars/door bars and roll bar together on Brett's car? Did he fab them up or....??

I have seen the swing-out bar ends used before (welded into the tubing ID) but not the receiving clamps that go over the tubing OD. Pretty slick.

Seems like a cool idea, easy to take the door bar sections in/out for doing the interior, etc...I'm wondering what the various sanctioning bodies would have to say about these...Since I see Brett has had the car out on the track quite a bit, maybe it has not been an issue...they look plenty stout.

http://inlinethumb10.webshots.com/17801/2243983840011691741S600x600Q85.jpg

[Steve1968LS2]

I did hear they have some sort of crazy mil-spec coating on the inside to give them additional bite. I seem to remember a figure of 500-ft-lbs or something like that.

I won't say more since I'm going off just memory but a LOT went into the design of those brackets. I'm sure and ART guy will drop in give the 411.

[XcYZ]

Rob, I'm almost certain that Brett told us at SEMA that you can (or will be able to soon) get the clamps individually.


Here's his thread introducing the Tiger Cage:

http://www.lateral-g.net/forums/showthread.php4?t=17276

[V8TV]

Straight from Bret...

http://v8tvshow.com/content/view/675/1/

[rwhite692]

I knew I would miss some cool stuff by skipping Sema this year!

Thanks guys, and hats off to Brett, he has certainly put a lot of thought, hard work, and tooling investment into this product! ...Definitely makes me consider the idea of selling the S&W cage I already have, and going with this.

[chicane]

Anyone know the story about the brackets or fittings holding the downbars/door bars and roll bar together on Brett's car?

I'm wondering what the various sanctioning bodies would have to say about these...Since I see Brett has had the car out on the track quite a bit, maybe it has not been an issue...they look plenty stout.

Lets start of with the fact that this is not a structural "roll" cage meant for rollover or impact protection. This product was designed for 'stiffening' up the chassis... at that is about all it can do. I have doubts that it will get any certification from the FIA or SFI... or the NHRA. Maybe the SCCA will give it something for low speed events but that itself would be questionable.

Current rules mandate:

All bolted structures shall have at least two bolts, 180 degrees apart, through support pads and roll cage structure brace connections.

So unless it is welded or utilizes two perpendicular fasteners, its a no-go. Since this clamp is rated to 450 lbs/ft of torsional loading, it doesn't seem to be much more useful than as to stiffen the chassis. The fact of the matter is that even in a low speed crash (45 mph or less) the impact load of a 3200+ lb car is about 10 times more than that of the clamps capacity... which is only rated to 450 lbs/ft. Basically... the clamp becomes the failure point in the event of an accident.

Moreover, the materials being used in this products construction, stainless 304, come's under some real scrutiny. Merely looking at a material from it's 'Ultimate tensile strength' alone is bad Ju-Ju... in consideration for a structural or safety aspect. Sure it does read nice that in the advertising that the product compares 304 stainless to 1020 steel... but the specifications that are actually being compared, means very little. What is important here is not the 'Ultimate tensile strength'... but the specific materials 'yield strength.' Also to take into consideration is that the UTS numbers deal with tension, not shear and its modulus of elasticity which are more characteristic in its failure mode, and more prevalent in roll cage modeling.

Let's define terms.

The "Ultimate tensile strength" of a material is the maximum tensile (stretching) load per unit of cross-sectional area that the material can withstand before rupture; strength represented in psi.

The "Yield strength" of a material is the tensile load per unit of cross-sectional area at which the material exhibits a specific limiting permanent set or elongation. It is thus different from, and greater than, the elastic limit; strength represented in psi.

The "Elasticity" is a property that a material exhibits by returning to its original size and shape after it has been deformed or strained by an applied stress. Each material has a definite point termed its 'elastic limit,' beyond which the material cannot be stressed without undergoing permanent distortion. The object in designing any structure is to keep the stress level at all times below the elastic limit of the material used. The elastic limit of a material is described as the maximum unit stress that the material can withstand without undergoing a deformation which will remain after the load has been released; strength represented in psi.

Lets compare what is really important (the following is from ASTM doccumentation):

304 stainless: UTS 73,200, yield 31,200

1020 steel: UTS 82,000, yield 70,000

4130 ChroMo normalized: UTS 97,200, yield 75,000 (Note: Only when it is properly heat treated will it yield over 100k psi. Nor will you heat treat a cage in a unitized chassis construction.)

So... what is shown here is that the 1020 steel has a more than a 100% increase, in the more important 'yield' strength, over that of 304. Also, this shows that using 4130 ChroMo for roll cage material is a waste of money. Because unless you actually heat treat the entire structure, it will not yield an amount over that of 1020 to make any kind of difference in this application. Basically, if you use 4130... you have a really expensive cage with the yield strength of 1020 but with brittle weldments.

I wont even go into the tubing size explaination used in the advertisement, as it doesnt hold it weight either.

Not to rain on the product Paul... but your advertisement is technically mis-leading.

[rwhite692]

OK... I'm pulling up a chair...& just put the popcorn in the microwave

Agree that the "stated purpose" is somewhat vague...From the ART Tiger Cage webpage:

"As with any “rollcage”, the main function and ultimate purpose of the TigerCage is to protect the occupants in case of a crash. However, its usefulness is more often expressed in stiffening and strengthening the car’s chassis."

Also on the same page:

"The primary function of the TigerCage is chassis stiffening. Any safety protection is strictly coincidental."

[chicane]

Yes... it may just. But please note... that I am not calling Paul out or calling the product junk. I just feel that what was written does not convey what really needs to be, or should be, stated.

I'll be out of pocket for the next three days... so by the time I get back, I am sure this will be somewhat interesting.

[mazspeed]

I'm curious on the tiger cage if it would stiffen the chassis enough for light to moderate road racing? In a crash it should provide some light protection I would think? no?

[Blown353]

Tom, you just saved me a lot of typing and the inevitable coming to my own defense after I was ready to post nearly exactly what you just did.

And I agree 100%... you're probably in for some fun 3 days from now. :lol:

At least they have disclaimers on their website and are not selling this as a bolt-in "roll" cage or item specifically intended for occupant safety. It remains to be seen how many consumers will either heed and/or overlook that disclaimer... it's a mighty important "one-liner" and I'm confident Bret & Co. will receive at least one irate call from an ill-informed customer who is upset his "roll cage" didn't pass tech inspection at the track.

At least I don't see shoulder harness hardpoints or a harness crossbar on the pictures on their website... things could get very interesting in the liability department in that case; I'm guessing the absence of a harness bar is not an accident.

[MtotheIKEo]

The door bars make it easy to get in and out but I think they are a lot lower than the sanctioning bodies would like.

[MarkM66]

At least I don't see shoulder harness hardpoints or a harness crossbar on it... things could get very interesting in the liability department in that case; I'm guessing the absence of a harness bar is not an accident.


I wonder what the shoulder harnesses are tied to.

[wiedemab]

I wonder what the shoulder harnesses are tied to.

They are attached to a bar that is just below the clamp for the door bars.

Is that low? I thought they were supposed to run straight back off the shoulders to avoid spine compression.

I know others know more about this than me, but I think I have read that somewhere. I guess you could move the bar up.

[Blown353]

They are attached to a bar that is just below the clamp for the door bars.

In the picture in the original post, that appears to be the case... but I didn't see any mention of harness attachments in the description on the webpage. However, in the webpage picture there appears to be harness tabs on the crossbar that is pushed all the way down near where the door bars clamp on.

Harness mounting specs vary by manufacturer, but usually the manufacturers want them anchored level (+/- a certain tolerance) with the harness passthrough provisions in the seatback, and I believe some sanctioning bodies specify their own requirements but I would hope they follow the testing and requirements set forth from the manufacturer. Some manufacturers such as Schroth have versions specifically for street cars that tie into the rear seat lap belt hardpoints (and have built in retractors), but using 4-point belts on a vehicle without rollover protection is another safety matter as well.

Here's a tech sheet regarding shoulder harness angle; they specify -5 to +30 degrees from the seat passthroughs for maximum effectiveness and to avoid spinal compression injury.

http://www.vickracing.us/technotes/SFI_Harness.pdf

[rwhite692]

Re the harness bar, I noticed this as well. On the webpage, the bar is shown mounted low (as low as it can go on the roll bar tubes) which, as previously stated, isn't correct. However at Sema, on both the display and in Brett's car, the harness bar is up near shoulder height.

[deuce_454]

so what was the word?? will the clamps be offered for sale without a cage, or wont they??? also what is the dimension of the stainless tubing??

[Swairlines]

Anyone know the story about the brackets or fittings holding the downbars/door bars and roll bar together on Brett's car? Did he fab them up or....??

I have seen the swing-out bar ends used before (welded into the tubing ID) but not the receiving clamps that go over the tubing OD. Pretty slick.

Seems like a cool idea, easy to take the door bar sections in/out for doing the interior, etc...I'm wondering what the various sanctioning bodies would have to say about these...Since I see Brett has had the car out on the track quite a bit, maybe it has not been an issue...they look plenty stout.

http://inlinethumb10.webshots.com/17801/2243983840011691741S600x600Q85.jpg

Can you PLEASE tell me where you got these seats? I'm hoping they are manufactured NOT custom....

Thx,

Jeff

[Flash68]

Can you PLEASE tell me where you got these seats? I'm hoping they are manufactured NOT custom....

Thx,

Jeff

.."custom Cerullo Seats"...

http://www.ridetech.com/garage/barret-jackson-2011-velocity/